The fact that smoking is injurious to health, no doubt: already proven link cigarette use and development of cardiovascular disease, lung disease, cancer. Smoking takes the lives of 6 million people each year worldwide.Scientists continue to find more and more negative consequences of this bad habit. Smoking causes changes in the work of more than 7000 genes.We are talking about DNA methylation - modification, in which the work of certain genes may be blocked. Because of this, the cell can no longer produce the substance and stops to perform a its function. These changes are called epigenetic and influence the activity of genes, increasing the work of some and repressing others. Many of these changes and can become a cause of occurrence of diseases associated with smoking.The authors examined data for analysis of blood samples taken from almost 16 thousand people who took part in 16 different studies. They found that some changes disappeared five years after smoking cessation, but some of them remained in the genome even after 30 years after people quit smoking. This means that the risk of many diseases retained even if the person stops smoking.